The calculation is rather involved. I would suggest you go to your library and check out a book by Peter Duffet-Smith called 'Practical Astronomy with your Calculator" published by Cambridge University Press back in 1981. He gives the step by step method for doing this and many other calculations having to do with apparent solar, lunar and planetary positions. Also, have a look at back issues of Sky and Telescope magazine. For the last 5 years or so, they have had a column by Bob Sinot on astronomical calculations and simple computer programs. He may have had an article on this. Also, check out the books described in Sky and Telescope. I know that 'astronomy on your computer and calculator' is a moderately popular topic.